A bee’s eye view of remarkable floral colour patterns in the south-west Australian biodiversity hotspot revealed by false colour photography

BACKGROUND AND AIMS Colour pattern is a key cue of bee attraction selectively driving the appeal of pollinators. It comprises the main colour of the flower with extra fine patterns indicating a reward focal point such as nectar, nectaries, pollen, stamens, and floral guides. Such definition of floral traits' advertisement guides visitation by the insects, assuring precision in pollen gathering and deposition. The study, focused in Southwest Australian Floristic Region (SWAFR), aimed to spot bee colour patterns that are usual and unusual, missing, accomplished by mimicry of pollen and anthers; and overlapped between mimic-model species in floral mimicry cases. METHODS Floral colour patterns were examined by false colour photography in 55 flower species of multiple highly diverse natural plant communities in southwest Australia. False colour photography is a method to transform a UV-photo and a colour photo into a false colour photo based on trichromatic vision of bees. This method results particularly effective for rapid screening of large numbers of flowers for the presence of fine-scale bee-sensitive structures and surface roughage that are not detectable using standard spectrophotometry. KEY RESULTS Bee-, and bird-pollinated flowers showed expected but also some remarkable and unusual previously undetected floral colour pattern syndromes. Typical colour patterns include cases of pollen and flower mimicry and ultraviolet-absorbing targets. Among the atypical floral colour patterns are unusual white and UV-reflecting flowers of bee-pollinated plants, bicoloured floral guides, consistently occurring in Fabaceae spp., and flowers displaying a selective attractiveness to birds only. In orchids' genera (Diuris and Thelymitra) that employ floral mimicry of model species we revealed a surprising mimicry phenomenon of anthers mimicked in turn by models species. CONCLUSION The study demonstrates the applicability of 'bee view' colour imaging for deciphering pollinator cues in a biodiverse flora with potential to be applied to other eco regions. The technique provides an exciting opportunity for indexing floral traits on a biome-scale to establish pollination drivers of ecological and evolutionary relevance.